Nutrients for Natives
by Jeanne McRight, Master Gardener | Certified Horticulturist
Location, location, location...
Indigenous plant species are adapted to their local habitat and ecology. Successful native gardens are composed of local plants grown in local soil (avoiding imported topsoil) and are supported by a healthy community of local native insects and soil organisms. Urban boulevards are suitable sites for native tallgrass prairie plants, many of which are salt-tolerant and adapted to clay soils and drought.
Soil Care and Repair
Organic soil amendments are key to the success of boulevard planting. The old adage “If you take care of the soil, the soil will take care of the plants” is very true in this harsh growing environment.
Organic matter performs two major functions in the soil: it improves soil structure for better soil aeration and moisture movement, and it nourishes beneficial microorganisms.
Add organic matter by top-dressing your garden with ample amounts of compost, leaf mold, and/or well-aged manure.
Nutrient levels - less is more
For boulevard locations, choose tallgrass prairie species appropriate for low nutrient conditions, including legumes whose nitrogen-fixing capability benefits their companions. Additional fertilizers reduce natives’ ability to outcompete weedy species and can cause root dieback and shoot burning.
pH affects nutrient levels: iron and manganese are less available in alkaline soils; phosphorous and potassium levels are low in acid sandy soils. Do not try to alter pH; instead, use native species adapted to those conditions. They will out-compete exotic invaders.
Soil restoration - dealing with compaction and salt
Boulevard soils are typically compacted, causing low infiltration and porosity levels that allow topsoil loss and water pollution. Planting deep-rooted “sod-buster” prairie native species and annual applications of compost will loosen compacted soil, improve its permeability and increase root access to nutrients, benefiting both plants and the environment.
Damage to boulevard gardens is caused in winter by deposited and airborne salt from road deicing equipment and traffic spray. Melting snow banks leave high concentrations of sodium and chloride in the soil. Roots become so damaged that they will not take up water. Plants growing in poorly-structured clay or compacted soils are more susceptible since the salt remains in the root zone. Tolerance is increased when drainage improves by adding ample organic matter. Then flushing with water will help leach excess salt away the root zone.
Feed The Fungi
Mycorrhizae fungi form a symbiotic relationship with plant roots and allowing plants to survive the stresses of extreme temperatures, drought, and soil infertility. Both mycorrhizal fungi and beneficial bacteria greatly reduce plant mortality from construction damage and soil compaction. When soil nutrients are depleted, mycorrhizae can greatly increase the root systems’ surface area, where their hyphae receive sugar exudates from the roots and release nutrients and water back to the plant.
Microbiota are locally adapted so it’s best to encourage your own garden population’s growth, rather than inoculating your soil with non-local species which may not flourish.
Inorganic fertilizers, especially those containing superphosphate, damage soil microbes populations and favor growth of weeds and nonnative species.
For those who are concerned about loss of biodiversity, establishing boulevard gardens using native plant species is a worthwhile and rewarding endeavor. The final product, healthy soil and a restored native community of plants and wildlife, is well worth the effort.
Find out More…
For helpful information on designing your garden and choosing site-appropriate native perennial species please see Your Blooming Boulevard, Part 1: Getting Started
Need tips on site preparation and establishing a new garden? Go to Your Blooming Boulevard, Part 2: From the Ground Up
Carolinian Canada Habitat Gardens for Climate-smart Communities (2018). Carolinian Canada Coalition. Retrieved from https://caroliniancanada.ca/
Dorner, Jeanette (2002). An introduction to using native plants in restoration projects. Plant Conservation Alliance, Bureau of Land Management, US Department of Interior U.S. Environmental Protection Agency. Retrieved from https://www.fs.fed.us/wildflowers/Native_Plant_Materials/documents/intronatplant.pdf.
Ontario Ministry of the Environment (2012). Soil Management – A Guide for Best Management Practices - Draft for Consultation. Toronto, Ontario. Retrieved from http://lakeridgecitizens.ca/lccw/wp-content/uploads/2013/06/MOE-BMP-on-EBR.pdf
Reinsch, C.T., Admiraal, D.M., Dvorak, B.I., Cecrle, C.A., Franti, T.G., Stansbury, J.S. (2007). Yard Waste Compost as a Stormwater Protection Treatment for Construction Sites. Water Environment Research. Vol. 79. No.8. Pp. 868-876. Retrieved from https://doi.org/10.2175/106143007X220545
Van Seters, Tim and Young, Dean (2012). Preserving and Restoring Healthy Soil: Best Practices for Urban Construction. The Sustainable Technologies Evaluation Program,Toronto and Region Conservation Authority. Retrieved from https://sustainabletechnologies.ca/home/urban-runoff-green-infrastructure/healthy-soils/preserving-and-restoring-healthy-soil-best-practices-for-urban-construction/